Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$12.94	9.542%	$14.1747	$14.17	$14.15	$14.20
Purchase #2	$90.91	10.508%	$100.4628	$100.46	$100.45	$100.50
Purchase #3	$17.30	12.596%	$19.4791	$19.48	$19.50	$19.50
Purchase #4	$181.81	12.167%	$203.9308	$203.93	$203.95	$203.90
Purchase #5	$170.89	11.563%	$190.65	$190.65	$190.65	$190.70
Purchase #6	$96.49	9.291%	$105.4549	$105.45	$105.45	$105.50
Purchase #7	$103.90	8.244%	$112.4655	$112.47	$112.45	$112.50
7 purchase totals =	$674.24		$746.6178	$746.61	$746.60	$746.80